1. Field of the Invention
The present invention relates to a rotating electric machine to be cooled by a coolant flowing inside of the rotating electric machine, and to a method of operating the same.
2. Description of the Related Art
There is conventionally known a rotating electric machine in which a coolant supplied into a hollow shaft is scattered by rotation of the hollow shaft itself to cool coil ends of a stator (see, for example, Japanese Patent Application Laid-open No. 2013-115848).
The following rotating electric machine is also known. The rotating electric machine includes a ring member provided on an outer circumference of a stator core and a case which houses the stator core and the ring member therein. A coolant is supplied between the ring member and the case so that the coolant is supplied to coil ends of a stator through holes formed through the ring member (see, for example, Japanese Patent Application Laid-open No. 2009-195082).
The rotating electric machines described in Japanese Patent Application Laid-open Nos. 2013-115848 and 2009-195082 both have a structure in which the coil ends of the stator are cooled. Therefore, although the coil ends of the stator are cooled actively, the remaining portion of the stator and a rotor provided on the inner side of the stator are not cooled actively. Thus, the above-mentioned rotating electric machines have a problem in that cooling efficiency as a whole is low.